Classification: Genetic
Mnemonic: Evo Devo Mutation
Specific Model: Developmental Mutation
Original Proponent(s): Filler (2007)    
Assessment: Popularity: Not listed. This is a new model that wasn't mentioned in any text surveyed.
Simple: #23 (=3) / 42 (52%)
Detailed: #34 (=2) /42 (49%)
Basic Summary: An early mutation pre-Morotopithecus was responsible for giving the whole great ape lineage a propensity to bipedalism.    
Discussion: Aaron Filler's thesis, published in a volume "The Urpight Ape - A New Origin of Species" in 2007,  is that a developmental mutation was responsible for a saltatory phenotypic change in the anatomy in vertebral anatomy in the hominoid lineage. Filler, who is a specialist in the spine and vertebral anatomy, suggests that the alteration immediately made an upright posture much more likely in the hominoid lineage.
More controversially, Filler argues that the fossil evidence from Morotopithecus, an African ape dated ca 20Ma, shows that they already had this mutation and were therefore already somewhat bipedal.
Filler makes some good arguments from the growing field of "evo devo" (evolutionary develomental biology) notably that there are many examples in evolution where the orientation of a given morphology appears to suddenly change, for example rotated through 180 degrees. And in that sense there can be little argument that such mutations affecting vertebral morphology are plausible.
However what is lacking from Filler's account is any discussion of an adaptive backdrop againsst which such mutations might either be neutral or exposed to positive or negative selection. It's the lack of attention to Darwinian natural selection that weakens the argument most. No one would doubt that mutations provide the necesary variation in genotypes but most commentators would assume that natural selction then works on that variation to consolidate those mutations into the gene pool.
 Strengths: Very straightforward and simple model. Falsifiable.    
Weaknesses: Does not offer any arguments from natural selection to back it up.    
1.1 Survival Value 0 (Poor) This model was rated poor by this criterion as it offers no Darwinian mode of selective advantage.    
1.2 Sexual Selection 0 (Poor) This model was rated poor by this criterion as it offers no means of sexual selection.    
1.3 Not Teleological 9 (Good) As this model posits that the switch to bipedalism was simply a mutation it has to be judged very highly by this criterion.    
2.1 Improved Food Acquisition 5  (Fair) This model was rated neutral by this criterion    
2.2 Accounts for Predation 5  (Fair) This model was rated neutral by this criterion    
2.3 Why Apes are not Bipedal 3 (Poor) As the proposed mutation is proposed to have occurred very early (pre-Morotopithecus) the opportunity for providing a simple solution to the question: why are only humans bipedal is not taken.    
2.4 Extant Analogues 5 (Fair) This model was rated neutral by this criterion    
2.5 Applies to Both Sexes 9 (Good) This model applies eqally well to both sexes.    
3.1 Hominid Anomalies 4 (Fair) This model was rated neutral by this criterion    
3.2 Fits Paleoecological Record 5 (Fair) This model was rated neutral by this criterion    
3.3 Precursor to Strider and knuckle Walker 8 (Good) The proposed mutation which resultied in a "diagograde" ape does provide a plausible and rather elegant precursor to both bipedalism and knucle-walking.    
4.1 Extended Explanatory Power 0 (Poor) This model only explains bipedalism as it based on a single rather simple mutation effecting the development of the spinal chord.    
4.2 Complimentary 5 (Fair) This model was rated neutral by this criterion    
4.3 Falsifiable or Testable 9 (Good) This is possibly the only falsifiable model of bipedalism as future better understanding of the genome of primates should allow us to determine exactly when suh mutations occurred and how they eefected primate phyolgeny.    
References Filler, A. (2007). The Upright Ape - A New Origin of the Species. New Page (Franklin Lakes)